Environmental DNA/RNA for pathogen and parasite detection, surveillance, and ecology

Approaches involving environmental DNA/RNA (eDNA/eRNA) – collectively eNA – can be used for pathogen discovery, ecology studies, surveillance, disease risk assessment, and early warning systems, after appropriate validation.eNA can provide evidence of the presence of pathogens in a system, and increases the spatiotemporal scope and efficiency of surveillance efforts – but it cannot, on its own, provide confirmatory evidence of infection of local hosts.The ‘pathogen eNA continuum’ provides a framework for designing pathogen eDNA/eRNA investigations, to elucidate pathogen life cycles, host reservoirs and vectors, and to link environmental detection to actual infections.Pathogen eRNA may provide additional insight into pathogen viability and activity, and can be used alternatively or in addition to eDNA.eNA approaches can be developed for predictive spatiotemporal modelling of pathogen distribution and impacts. Detection of pathogens, parasites, and other symbionts in environmental samples via eDNA/eRNA (collectively eNA) is an increasingly important source of information about their occurrence and activity. There is great potential for using such detections as a proxy for infection of host organisms in connected habitats, for pathogen monitoring and surveillance, and for early warning systems for disease. However, many factors require consideration, and appropriate methods developed and verified, in order that eNA detections can be reliably interpreted and adopted for surveillance and assessment of disease risk, and potentially inclusion in international standards, such as the World Organisation for Animal Health guidelines. Disease manifestation results from host–symbiont–environment interactions between hosts, demanding a multifactorial approach to interpretation of eNA signals.